This invention relates to an improved remote fluid transfer system for marine structures. More specifically, this invention relates to an improved remote fluid transfer packer inflation and grouting system for offshore platforms installed in deep waters where the offshore platform is anchored in position utilizing anchor pads on the sea floor or requires a remote fluid transfer system to reduce piping complexity and cost due to the size of the platform.
As offshore platforms were installed in deeper waters, it ultimately became necessary to start filling the annulus between the jacket leg and piling driven therethrough of the platform with grouting material in an attempt to add strength and rigidity to the platform. At first, these grouting jobs were run either by pumping grout into the top of the jacket leg hoping that the grout would form an annular plug and displace the water from the jacket leg as it moved downwardly therethrough or by running lines to the bottom of the jacket leg where an initial grout plug was installed in the jacket leg and left to harden with subsequent grout being placed thereon utilizing a line connected to the jacket leg above the initial grout plug. A typical example of the later grouting method and apparatus is shown in U.S. Pat. No. 3,564,856 to Blount et al.
As problems were encountered with placing grout into the water filled annulus between the jacket leg and piling driven therethrough, various grouting procedures were developed to place grout into the annulus after it has been dewatered. One type of grouting procedure involved dewatering the leg using compressed air or gas, then setting a grout plug to harden to subsequently add grout in subsequent stages on top the plug to fill the annulus Examples of this procedure are shown in U.S. Pat. Nos. 3,492,824 and Re. 28,232. However, since any supported plug method of grouting is subject to the initial grout plug falling out from the jacket leg in soft or muddy bottoms or no sea bottom at all being present around the jacket leg, various types of grouting procedures using mechanical or inflatable grout seals have been developed.
When using a mechanical or inflatable grout seal installed on the bottom of a jacket leg, grout is injected into the annulus in one or more stages starting from the bottom of the jacket adjacent the grout seal and as the grout flows into the annulus between the jacket leg and piling the grout displaces the water in the annulus out the top of the jacket leg. Grout is continued to be pumped into the leg during grouting operations until grout having the desired density exits the top of the jacket leg. Similarly, where mechanical or unflatable grout seals are used on pile sleeves, sleeves connected to the lower portion of the jacket having piling driven therethrough and used to add strength and stability to the platform, grout is pumped into the bottom of pile sleeve annulus adjacent the grout seal displacing the water in the annulus out the top thereof with a predetermined excess amount of grout continuing to be pumped into the annulus to over fill the same.
An early example of an inflatable grout seal used in offshore platform grouting operations in shown in U.S. Pat. No. 3,468,132. An advantage that inflatable grout seals have over mechanical grout seals, such as shown in U.S. Pat. No. 3,702,537, is that inflatable grout seals are capable of supporting a grout column hundreds of feet in length in the jacket leg annulus during grouting operations while mechanical grout seals are capable of supporting grout columns having a length of only approximately 10 feet to 50 feet typically, thereby requiring a second stage of grout to be placed on top the short hardened grout plug to fill the jacket leg annulus.
After inflatable grout seals were developed, in order to reduce the number of separate inflation lines running to each inflatable grout seal and grout lines running to jacket legs and pile sleeves on offshore platforms, systems utilizing a single line to inflate an inflatable grout seal and supply grout to a pile sleeve, or jacket leg, were developed. Such systems are typically illustrated in U.S. Pat. Nos. 4,063,421, 4,063,427, 4,077,224, and 4,140,426.
However, such single line inflation and grout systems suffer the disadvantage that it is not known whether the inflatable grout seal is properly inflated or has failed until after grout has been pumped into the pile sleeve or jacket leg annulus and the calculated amount of grout does not fill the annulus thereby requiring more grout or alternative grouting systems to be used.
In other attempts to reduce the number of grout lines and inflation lines for grout seals on platforms, particularly as offshore platforms became larger and more complex, two different approaches have been pursued.
One approach was to place a grout manifold at a remote location on the platform and have a diver intermittently connect a flexible line, such as a rubber hose, from the surface to the desired grout line. Such a system for grouting purposes only is shown in U.S. Pat. No. 4,214,843. However, for platforms in deep water it may be too difficult or too deep for a diver to connect a flexible grout line to a grout manifold or to open and close any valves used in back-up grouting systems if the primary grout system fails.
Another approach to reducing the number of grout lines and inflation lines for inflatable grout seals, is to use control valves in the grout system and inflation system so that multiple pile sleeves or jacket legs can be grouted through a single line running to the surface of the offshore platform and multiple inflatable grout seals may be inflated and tested using a single inflation line running to the surface of the offshore platform. Such inflation an grout systems are shown in U.S. Pat. No. 4,275,974. Although these types of inflation and grout systems work well and are cost effective, for any offshore platforms, inflation and grout lines still must be run to the top of the offshore platform and relied on for inflation and grouting purposes.
For deep waters it may be desired to have a floating drilling platform, production platform or other moored platform, rather than a conventional offshore platform resting on and being secured to the sea floor by piling driven through the jacket legs and pile sleeves connected thereto. Such floating structures are suggested in U.S. Pat. Nos. 3,154,039, 3,648,638, 3,780,685 and 3,919,957. Typically, such floating platforms utilize anchors to retain them in position. The anchors are typically structures utilizing, in turn, either ballasting and deballasting means to control and determine their position on the sea floor or piling driven through sleeves on the structure which is secured to the structure by grouting the sleeve annulus.
As floating platforms having anchors comprising structures utilizing piling are installed in greater water depths it has become necessary to devise apparatus and methods which would allow the remote placement of the fluids and other types of materials and grouts, and the like for securing the anchors in position.
One such apparatus and method being marketed by Wimpey Laboratories Limited and Oil States Industries Division, LTV Energy Products, discloses a system for grouting and inflating inflatable grout seals on a subsea template. The Wimpey system substitutes a remotely operated vehicle for a diver to remotely manipulate the end of a rubber hose to insert a stinger into or onto a receptacle for supply grouting material to a grout system or inflation fluid to an inflation system for inflatable grout seals and to manipulate various valves and connectors in the grout system and inflation system. One of the advantages offered by this arrangement is that the umbilical flexible hose line, a rubber hose, can be retained on a reel on a vessel and easily, quickly deployed along with a clump weight, to control buoyancy, from the vessel. However since the system utilizes permanent connectors to connect the umbilical flexible hose line to the receptacles, it is necessary to retrieve and replace the receptacle each time the grouting of a sleeve or inflation of an inflatable grout seal has been completed. Also, since this type of system replaces a diver with remotely operated vehicle, R.O.V., the R.O.V. must be used to make connections with the umbilical line, disconnect the umbilical line, guide the umbilical line, and operate various valves in the inflation system and grout system. In waters with currents and where the umbilical line is difficult to handle the R.O.V. may have to include multiple arms to cling to the template to maintain its station. Additionally, is has been found that with a neutral or slightly negative buoyancy umbilical line that it is difficult to make the connections between the male and female portions of the connectors and that if a negative buoyancy umbilical line is used, to assist in making connections, stresses quickly mount on the umbilical line thereby limiting the depths at which it can be safely used and thereby making the umbilical line difficult or impossible for the R.O.V. to handle. Furthermore, if the pneumatic type connectors are used, the umbilical line handling problems are increased as there are two separate flow lines making up the umbilical for the R.O.V. to handle and control.
Another apparatus and method proposed for use in the grouting operations and inflating inflatable grout seals on a subsea template is disclosed in United Kingdom Pat. No. 2,096,674. In this system for remotely operating a grout system and inflating an inflatable grout seal system, the remote system includes a conduit string suspended from a derrick barge from a cantilevered work platform containing a hydraulic snubbing unit with the conduit string including a remote video camera secured to the conduit string, an orientation jet assembly secured to the conduit string to move the conduit string for insertion into a sleeve receptacle and a stinger assembly located on the end of the conduit string to sealingly engage a portion of the sleeve receptacle to allow fluid transfer thereto. The grouting system attached to the subsea template includes at least one sleeve receptacle which releasably receives a portion of the stinger assembly therein and flow lines interconnecting the sleeve receptacle with at least one annulus between a pile sleeve and a pile driven therethrough. The system also includes an inflation system for inflating an inflatable grout seal located on a pile sleeve from the sleeve receptacle. The inflation system includes a flow line from the sleeve receptacle to the inflatable grout seal on the pile sleeve, the flow line including a check valve and flow control device or means therein and a dummy sleeve receptacle in which the conduit string having the stinger assembly on one end thereof can be placed when it is not being used in either inflating inflatable grout seals or grouting the pile sleeves. Also, a slip joint may be included in the conduit string to compensate for motion of the derrick barge.
While the remote fluid transfer system has desirable features, it also has undesirable ones. For instance, since the hydraulic snubbing unit does not allow for significant horizontal movement of the conduit string, the conduit string must be first positioned at the desired location on the subsea template by moving the derrick barge. Then, the conduit string is guided into the desired receptacle by pumping through the orienting jet assembly. In another instance, since the remote video camera is secured to the conduit string, it has a limited field of view and, more significantly, does not include any position referencing device thereby making it difficult to determine the location of the conduit string with respect to the subsea template and the manner in which the conduit string should be manipulated to insert the stinger assembly into the desired sleeve receptacle. Additionally, since the remote video camera is located on the conduit string the conduit string then must have the video cable secured thereto making it difficult to assemble and manipulate with the slip joint and any safety joint included therein.
All these make the remote fluid transfer system overly complex, not easily subject to manipulation for insertion into the sleeve receptacle, and difficult to use. The system is overly complex because it has all the necessary components assembled into or onto a single conduit string to be manipulated remotely, the system is not easily subject to manipulation because it is suspended from a hydraulic snubbing unit on a cantilevered work platform secured to a derrick barge thereby causing the derrick barge to be moved to position the conduit string over the subsea template, and the system is difficult to use because the remote video camera is secured to the conduit string limiting the field of view of the camera and does not contain any reference system to determine the location of itself and of objects in its field of view.